Thermally operable flasher units



April 29, 1969 A. D. PRIICKETT 3,4 9

THERMALLY OPERABLE FLASHER UNITS Filed March 10, 1967 United States Patent 3,441,890 THERMALLY OPERABLE FLASHER UNITS Alfred Donald Prickett, Handsworth Wood, Birmingham, England, assignor to Joseph Lucas (Industries) Limited, Birmingham, England Filed Mar. 10, 1967, Ser. No. 622,331 Claims priority, application Great Britain, Mar. 30, 1966, 14,040/66 Int. Cl. H01h 61/08, 81/02 U.S. Cl. 337-138 4 Claims ABSTRACT OF THE DISCLOSURE A flasher unit for controlling the indicator lamps of a road vehicle, including a resilient vane which can snap from a first stable position to second stable position when lateral bending forces are applied to it. The vane is controlled by a thermally expansible strip connected in the indicator lamp circuit of the vehicle and the snapping of the vane between its stable positions is utilized to make and brake the indicator lamp circuits. The particular form of the vane is claimed.

This invention relates to thermally operable flasher units, for controlling the direction indicator lamps of a road vehicle.

A flasher unit according to the invention includes a base, a resilient vane having a substantially U-shaped slot therein which defines in the vane an integral finger through which the vane is secured to the base, the vane being formed with a rib which is axially aligned with the finger and which extends between an edge of the vane and the base of said slot, so that the vane has a first stable configuration which it assumes at rest, and a second stable configuration which it assumes when subject to stresses tending to 'bend the vane about a lateral axis, a thermally extensible strip engaged with the vane and which when cold subjects the vane to said stresses, a movable contact carried by said strip and a fixed contact engageable by said movable contact when the vane is in its second configuration, said strip and said movable and fixed contacts being connected in use in the direction indicator lamp circuit of a road vehicle so that when said circuit is energised current flowing through the strip and the fixed and movable contacts causes heating of the strip which expands allowing the member to assume its first configuration wherein the circuit is broken so permitting the strip to cool and contract thereby returning the member to its second configuration wherein the circuit is again completed.

One example of the invention is illustrated in the accompanying drawings wherein;

FIGURE 1 is a plan view of a flasher unit,

FIGURE 2 is a sectional view to an enlarged scale on the lines 22 in FIGURE 1, and

FIGURE 3 is a diagram of an electrical circuit utilising the flasher unit illustrated in FIGURES 1 and 2.

Referring first to FIGURES 1 and 2 the flasher unit comprises an insulating base 11 moulded in a synthetic resin material and having a short integral post 12 upstanding from the upper face thereof. Supported on the post 12 and extending at right angles thereto is a conductive arm 13 which carries, at its end remote from the post 12, a contact 14. The arm 13 is electrically connected to a terminal blade 15 which is secured to the lower face of 'base 11. A second terminal blade 16 is also secured to the lower face of the base 11 and is electrically connected to a conductive rod 17 which extends through the base 11 and projects from the top face thereof.

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There is further provided a vane comprising a generally rectangular sheet of spring steel 18 formed with a U- shaped slot 19 which defines a rectangular finger 21 disposed centrally of the sheet. The sheet 18 is also formed with an embossed rib 22 aligned with the finger 21, and extending across the portion 20 of the sheet between the base of the slot 19 and a short side of the sheet. The sheet 18 is provided with a pair of tongues 23, 24 which extend from opposite ends of the sheet and which are formed with stepped portions 25, 26 the tongues 23, 24 defining raised platforms at both ends of the sheet. The portions 25, 26 extend upwardly from the same side of the sheet as the rib 22.

The free end of the finger 21 is secured to the end of the rod 17, the arrangement being such that the sheet 18 extends substantially parallel tothe top face of the base 11. The formation of the rib 22 urges together, and imparts a twist to, the limbs 18a, 18b of the sheet 18 and it is found that if such a sheet is secured at the free end of its finger 21 to a fixed support and forces are applied to the sheet to bend the sheet about a lateral axis in such a direction that the tongues 23, 24 would eventually touch, the sheet 18 will bend about an axis which passes through the junction of the finger 21 with the sheet 18 and moreover the sheet 18 will snap rapidly from a first position in which the limbs 18a, 18b extend in the plane of the finger 21 to a second position in which the limbs 18a, 18b are curved upwardly out of the plane of the finger 21. When such bending forces are removed with the sheet in its second position the sheet will snap rapidly back form its second position to its first position.

The sheet 18 is urged to its second position and a thermally extensible electrically conductive strip 27 is welded at its ends to the tongues 23, 24 so that while the strip is cold it holds the sheet 18 in its second position. A contact 28 is secured to the centre of the upper surface of the strip 27 and the arm 13 is bent so that the contact 14 engages the contact 28.

Referring now to FIGURE 3 the terminal blade 16 is connected to one terminal of the battery 31 of a motor vehicle, the other battery terminal being earthed. The terminal 15 is connected to the movable contact of a direction indicator switch 32 whereby the direction indicator lamps 33 of the vehicle can be energised. When the switch 32 is in an operative position current flows through the sheet 18 and strip 27, and the contacts 28, 14 and illuminates the appropriate lamps 33. However the current flowing in the strip 27 causes it to heat up and expand. The expansion of the strip 27 allows the sheet 18 to snap back to its first position and in so doing moves the contact 28 out of engagement with the contact 14 thereby cutting off the flow of current through the strip 27 and extinguishing the lamps 33. Since the strip 27 now has no current flowing in it, it cools and contracts so that the sheet 18 snaps once more to its secend position and in so doing re-establishes the electrical circuit to the lamps 33. This cycle continues until the switch 32 is opened.

Having thus described my invention what I claim as new and desire to secure by Letters Patent is:

1. A thermally operable flasher unit for controlling the direction indicator lamps of a road vehicle including a base, a resilient vane having a substantially U-shaped slot therein which defines in the vane an integral finger through which the vane is secured to the base, the vane being formed with a rib which is axially aligned with the finger and which extends between an edge of the vane and the base of said slot, so that the vane has a first stable configuration which it assumes at rest, and a second stable configuration which it assumes when subject to stresses tending to bend the vane about a lateral axis,

a thermally extensible strip engaged with the vane and which when cold subjects the vane to said stresses, a movable contact carried by said strip and a fixed contact engageable by said movable contact when the vane is in its second configuration, said strip and said movable and fixed contacts being connected in use in the direction indicator lamp circuit of a road vehicle so that when said circuit is energised current flowing through the strip and the fixed and movable contacts causes heating of the strip which expands allowing the member to assume its first configuration wherein the circuit is broken so permitting the strip to cool and contract thereby returning the member to its second configuration wherein the circuit is again completed.

2. A unit as claimed in claim 1 wherein the vane is conductive and in use forms part of the direction indicator circuit.

5 the rib is embossed on the vane.

References Cited UNITED STATES PATENTS 2,828,385 3/1958 Malone 337-89 10 2,907,850 10/1959 Colombo 33792 3,364,322 1/1968 Siiberg 337-92 BERNARD A. GILHEANY, Primary Examiner.

15 R. L. COHRS, Assistant Examiner.

US. Cl. X.R. 33792 

